Practical tools for measured work
Drawer Box & Slide Clearance Calculator
Size a drawer box from the cabinet opening and slide length, then send the parts to a cut optimizer.
the finished opening the drawer must fit into
nominal rail/slide length
how much shorter the box is than the slide
combined clearance both sides - undermount is typically tighter than side-mount
groove distance from each edge
The two sides and the front/back are the same strip height (100 mm) cut to different lengths - send them straight to the Linear Cut List Optimizer. The bottom panel is a sheet part - send it to the Plywood Cut Calculator.
How it works
How to use it: enter the cabinet opening width, your slide's nominal length, and your material thickness and clearances. This models a "captured" drawer box: two full-depth side panels, with the front and back panels fitted between them, and a bottom panel set into a groove inset from all four edges - the most common shop-built drawer box construction.
Formula.
Box width = opening width − total side clearanceBox depth = slide length − depth setbackFront/back length = box width − 2 × side thicknessBottom width = box width − 2 × bottom inset, Bottom depth = box depth − 2 × bottom inset
Worked example. With the defaults (450 mm opening, 450 mm slide, 25 mm depth setback, 13 mm total side clearance, 12.7 mm side thickness, 6 mm bottom inset): box width = 450 − 13 = 437 mm; box depth = 450 − 25 = 425 mm; front/back length = 437 − 2×12.7 = 411.6 mm; bottom = (437 − 2×6) × (425 − 2×6) = 425 × 413 mm.
Limitations
This models one common construction method - a captured box with an inset-groove bottom - not every drawer-box style. Applied (screwed-on) bottoms, dovetailed boxes, and overlay drawer fronts mounted proud of the box all change these numbers. It does not model a specific hardware manufacturer's published clearance chart; side clearance and depth setback vary meaningfully between undermount, side-mount, and different slide series, so treat the defaults as a starting point and confirm against your actual slide's installation instructions.
Drawer box height here is a direct input, not derived from the cabinet opening height - how much of the opening height a drawer box actually uses depends on face-frame or frameless construction, top/ bottom rail width, and reveal gaps, which this tool does not model.
Frequently asked questions
What side clearance should I use?
It depends on your slide type - undermount slides commonly need roughly 13 mm (1/2 in) total, while side-mount slides commonly need roughly 25 mm (1 in) total, but exact figures vary by manufacturer and series. Check your slide's installation instructions for the specific clearance it requires.
Why is the drawer box shorter (in depth) than the slide?
Slides need a small amount of travel and mounting clearance behind the drawer box so it doesn't strike the back of the cabinet when fully closed, and so the box doesn't over-extend the slide's rated travel when fully open. The depth setback captures that margin.
Can I use this for a different bottom-panel construction?
If your bottom panel is screwed to the underside of the box (an applied bottom) rather than set into a groove, set the bottom inset to 0 and use the box width and box depth directly as the bottom panel size instead of the computed bottom dimensions.
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